Corrosion inhibiting lubricant composition



United States Patent Ofiiice 3,505,228 Patented Apr. 7, 1970 3,505,228 CORROSION INH BITING LUBRICANT COMPOSITION Hayward R. Baker, Silver Spring, Md., and Robert N. Bolster, Fairfax County, Va., assignors to the United States of America as represented by the Secretary of the Navy No Drawing. Filed Apr. 24, 1968, Ser. No. 723,882 Int. Cl. C10m 1/32 U.S. Cl. 252-5l.5 7 Claims ABSTRACT OF THE DISCLOSURE Liquid compositions which are solutions in a volatile hydrocarbon solvent, such as n-hexane, of a lubricating oil, an antioxidant for the lubricating oil, a lower alkanol such as ethanol, and a reaction product which is prepared by heating a monoalkyl or monoalkenyl succinic anhydride with a primary or secondary long chain alkylamine in a ratio of from about 1.5 to 1.9 equivalents of the hydrocarbyl succinic anhydride per equivalent of the alkylamine and in the presence of an excess of the lower alkanol to form a solution having a temperature in the range of from about 50 C. to 5 C. below the boiling point of the alkanol. The liquid compositions are useful for providing a soft, non-tacky, solid coating of corrosion inhibitor and lubricant on metal surfaces. Additionally, they may be applied to displace water from wet metal surfaces.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The invention relates to new liquid compositions which are useful for displacing Water from metal surfaces and providing a corrosion inhibitor and lubricant on metal surfaces in the form of a soft, non-tacky solid coating.

BACKGROUND OF INVENTION Materials heretofore used for providing corrosion inhibiting coatings are not generally suitable for use on equipment which is handled in use and has parts which move in frictional contact, such as military small arms. A film of the corrosion inhibitor alone is usually too thin to provide sufficient lubrication. Coatings in which the corrosion inhibitor is contained in a wax vehicle are hard or viscous and as such would impede the operation of moving parts. Oily to tacky coatings which contain the corrosion inhibitor are objectionable when the equipment has to be handled and are conductive to pickup of sand and dust which results in wear and malfunction.

It is an object of the present invention to provide new corrosion inhibiting and lubricating compositions which are suitable for use on equipment which has to be handled in use.

It is also an object to provide new compositions of the aforesaid kind which additionally are effective to displace water from metal surfaces.

STATEMENT OF INVENTION The above and other objects are accomplished in the new compositions of the invention which, broadly stated, comprise a corrosion inhibitor which is a reaction product hereinafter more fully described, a lubricating oil and a water-displacing agent which is a lower alkanol.

The reaction products which constitute the corrosion inhibitors for the new compositions are obtained by heating a C to C alkyl or alkenyl succinic anhydride in admixture with a C to C primary or secondary alkylamine in the ratio of from about 1.5 to 1.9 equivalents of the hydrocarbyl succinic anhydride per equivalent of the alkylamine and in the presence of an excess of a C to C alkanol to form a solution at a temperature in the range of from about 50 C. to about 5 C. below the boiling point of the alkanol. Solution occurs quickly at these temperatures. Once the solution is formed, reaction takes place to form the reaction product.

In the reaction between the hydrocarbyl succinic anhydride and the alkylamine, the anhydride ring is split with formation of mixed isomers of an alkylamine salt and of an alkyl ester of the hydrocarbyl succinic acid alkyl half-amide. The alkyl portion of the ester group is derived from the alkanol. Small amounts of the unreacted hydrocarbyl succinic anhydride will usually be present in the reaction product. The reaction products constituting the corrosion inhibitor components for the compositions of the invention are comprised predominantly of mixed isomers in varying proportions of a C to C alkylamine salt and a C to C alkylester of a C to C alkyl or alkenyl succinic acid C to C alkyl half-amide.

The alkanol used in forming the reaction products may be ethanol, propanol or isopropanol. It is used in an excess which may be from about 2 to 3 times the combined weight of the starting alkyl or alkenyl succinic anhydride and alkylamine to provide a diluent for the reaction and the water-displacing agent in the new compositions. The alkanol may be used dry or contain water in amounts which do not result in the compositions containing more than 2% by weight of water.

The lubricating oil in the new composition may be a mineral oil or a synthetic lubricating oil, for example, an ester oil such as 2-ethylhexylsebacate and the mixed C -C monocarboxylic acid esters of pentaerythritol. The lubricating oil may be present in the compositions in amounts which are from about 40 to 60% by weight of the reaction product therein. Together, the lubricating oil and the reaction product content of the compositions may range from about 10 to 25% by weight thereof.

To protect the lubricating oil against oxidation, a small amount, about 0.15% by weight, of an antioxidant is included in the compositions. Suitable antioxidants are the known 2,6-di(tertiarybutyl) p-cresol and 2,4-dimethyl-6- tertiarybutylphenol.

The compositions of the invention are clear solutions of from about 6 to 10% by weight of a reaction product as defined above, from about 20 to 30% by weight of a C to C alkanol, from about 4 to 15% by weight of a lubricating oil and a small amount, about 0.15% by weight, of an antioxidant for the lubricating oil in a volatile hydrocarbon solvent having a boiling point in the range of from about 60 to C., for example, n-hexane and n-heptane. The volatile hydrocarbon solvent is the vehicle for application of the compostions and may be used in varying amounts, for example, from about 45 to 70% of the compositions. Water may be present in the compositions but not in amounts which would cause precipitation of the reaction products from solution. Permissible amounts of water in the compostions are up to about 2% by weight.

The new compositions are applied as a spray to metal surfaces to be coated, such as steel, stainless steel aluminum and brass surfaces of military small arms, to deposit thereon a corrosion inhibiting and lubricating coating which, on evaporation of the solvents dries to a soft, solid film having a wax-like (non-tacky) surface which is easy to handle and offers little adhesion to sand and dust particles. The deposited coating bonds to the metal surfaces through the polar amide, ester and amine salt groups of the reaction product component of the composition. When the coating is subjected to the shearing action of metal parts moving in frictional contact the structure of the coating breaks down to a grease-like consistency, offering lubrication and little resistance to the moving parts. Where the metal surfaces are wet with a film of water, the alcohol component of the applied composition will function to displace this water from the surface to provide a dry metal surface to which the solid coating will bond. The coatings so applied have the additional advantage of protecting adjacent scratched areas of metal through spread of lubricating oil thereto.

PREPARATION OF THE REACTION PRODUCT The reaction products which constitute the corrosion inhibitors of the compositions of the invention and which, additionally, provide, for the most part, the structure of the non-tacky, soft, wax-like solid coatings on metal surfaces sprayed with the compositions are prepared from alkyl or alkenyl succinic anhydrides of the formula:

where R is an alkyl or alkenyl radical of from 8 to 18 carbon atoms which may be normal or branched, for example, octyl, decyl, dodecyl, tetradecyl, hexadecyl, heptadecyl, octadecyl, Z-ethylhexyl, isostearyl, etc., octenyl, decenyl, dodecenyl tetradecenyl, hexadecenyl, heptadecenyl, octadecenyl, tetrapropenyl etc. and a primary or secondary alkylamine of the formula:

where R is an alkyl radical having a straight chain of from 18 to 22 carbon atoms and R is hydrogen or an alkyl radical having a straight chain ofi from 18 to 22 carbon atoms. When a mixture of the alkyla'mines is used for the preparation of the reaction products a random occurrence of the alkyl radicals in the alkylamine salt and alkylamido portions of the molecule of the formed mixed isomers will take place. Preferred amines for the preparation of the reaction products are the primary C to C alkylamines.

The preparation of the reaction products is illustrated by the following specific example. While a mixture of the alkylamines was used, the preparation is the same for making the reaction products using the individual alkylamines as defined above. Although water was added in preparing the reaction product such is not necessary and the dry alkanol may be used.

EXAMPLE To approximately 30 ml. of ethanol (water, 0.46 gram and ethanol, 23.53 grams, approximately) was added 4.58 grams of tetrapropenyl succinic anhydride (Monsanto- T PSA) and 6 grams of commercial mixed primary amines (Kemamine P190) composed of about 90% by weight of mixed arachidyl (C amine and behenyl (C amine and about by weight of stearylamine. The weight ratio of the arachidylamine to the behenylamine in the mixture was about 40% to 60%, respectively. The re- Sulting mixture, containing the hydrocarbyl succinic anhydride and the mixed alkylamines in a equivalent ratio of 1.8 to 1, respectively, was warmed to 50 C. under stirring to form a solution which was accomplished in about 2-3 minutes heating time.

To the solution in ethanol of the reaction product obtained in the above example Was added, 11.96 grams of petroleum lubricating oil (symbol 1010), 0.15 gram of 2,6-di(t-butyl)p-cresol and 53.32 grams of n-heptane and the whole mixed to form a clear solution. This solution embodies a preferred formula of the compositions of the invention.

The composition solution, prepared as above, was sprayed on water-wet steel plates and found to provide a soft, wax-like solid coating after evaporation of the solvents. A further portion of the composition solution was sprayed on a submachine gun to coat the metal parts, including the moving parts. After the solvents had evaporated, to leave a soft, wax-like solid coating on the metal surfaces, the coated gun was submerged for a half-hour in synthetic sea water in a pressure tank under an applied pressure equivalent to a ZOO-foot head of water. The wet submachine gun was withdrawn from the sea water and wrapped in a plastic bag to retain the water on the gun and allowed to stand in this condition for 3 days. The gun was then examined for evidence of corrosion of the metal surfaces and a few small spots of rust were found here and there. They were not such as to cause malfunction of the gun. Metal surfaces of a subrnachine gun were coated in the field from a composition solution prepared as above. The coated gun was hand immersed in the surf, withdrawn, and laid on the dry sand of the beach to determine sand pickup by the coating. The amount of sand which adhered to the coating was substantially less than would have adhered to a Cosmoline or the like oily coating heretofore used on guns.

Since the invention described herein may be variously practiced without departing from the spirit or scope thereof, it is intended that specific embodiments appearing in the above description shall be taken by way of illustration and not in limitation except as may be defined in the appended claims.

What is claimed and desired to be secured by Letters Patent of the United States is: s 1. A liquid composition comprising from about 45 to 70% by weight of a volatile hydrocarbon solvent having a boiling point in the range of from about 60 to C., from about 20 to 30% by weight of a C to C alkanol, from about 4 to 15% by weight of a lubricating oil, a small amount of an antioxidant for the lubricating oil, and from about 6 to 10% by weight of a reaction product prepared by heating a hydrocarbyl succinic anhydride of the group consisting of C to C monoalkyl and C to C monoalkenyl succinic anhydrides in admixture with an alkylamine of the group consisting of primary and secondary alkylamines having a straight chain of from 18 to 22 carbon atoms in a ratio of from about 1.5 to 1.9 equivalents of the hydrocarbyl succinic anhydride per equivalent of the alkylamine and in the presence of an excess of a C to C alkonal to form a solution having a temperature in the range of from about 50 C. to 5 C. below the boiling point of the alkanol, said excess of the alkanol being sufficient to provide the alkanol in the composition.

2. A liquid composition as defined in claim 1, wherein the volatile hydrocarbon solvent is n-heptanol.

3. A liquid composition as defined in claim 1, wherein the alkanol is ethanol.

4. A liquid composition as defined in claim 1, wherein the alkylamine is a primary C to C alkylamine.

5. A liquid composition as defined in claim 1, wherein the hydrocarbyl succinic anhydride is tetrapropenyl succinic anhydride.

6. A liquid composition as defined in claim 5, wherein the alkylamine is a primary C to C alkylamine.

7. A liquid composition as defined in claim 5, wherein the alkylamine is octadecylamine, arachidylamine and behenylamine in a mixture in which the arachidyl and behenylamines together are in preponderant amount.

References Cited UNITED STATES PATENTS 2,715,108 8/ 1955 Francis. 2,783,206 2/ 1957 Messina. 2,977,309 3/ 1961 Godfrey et al.

DANIEL E. WYMAN, Primary Examiner W. J. SHINE, Assistant Examiner US. Cl. X.R. 252-392 

